1. Field of the Invention
The invention relates to phenolic polynuclear compositions useful as intermediates for the formation of photoactive compounds. Further, the invention relates to such photoactive compounds formed by the esterification of these phenolic compositions with sulfonyl halides of naphthoquinone diazide. Still further, the invention relates to radiation sensitive mixtures useful as positive-working photoresists containing the combination of these photoactive compounds with alkali-soluble phenolic resins and solvent. Finally, the invention relates to substrates coated with these radiation sensitive mixtures and the process of coating, imaging and development of these mixtures on the substrate.
2. Description of the Background Art
Photoresists are photosensitive films used for transfer of an image to a substrate. They may be negative or positive acting. After a coating of a photoresist is formed on a substrate, the coating is selectively exposed through a photomask to a source of activating energy such as ultraviolet light. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. The pattern in the photomask of opaque and transparent areas define a desired image to be transferred to a substrate. A relief image is provided upon development of the latent image patterned in the resist coating. The background and use of photoresists are generally described, for example, in Deforest, Photoresist Materials and Processes, McGraw Hill Book Company, New York (1975), and by Moreau, Semiconductor Lithography, Principles, Practices and Materials, Plenum Press, New York (1988).
Various attempts have been made to alter the make-up of photoresist compositions to improve performance or functional properties. In particular, a variety of photoactive compounds have been reported including photoactive compounds that contain more than one diazoquinone moiety. It has been found, however, that many of such prior photoactive compounds exhibit undesirable properties and hence can be unsuitable for use in many resist formulations. For example, it has been reported that photoactive compounds having multiple photoactive groups exhibit poor solubility in typical photoresist solvents, limiting the shelflife of a resist containing such photoactive compounds. See, e.g., European Published Patent Application 0126266A2, incorporated herein by reference.
It thus would be desirable to have new polynuclear compounds and new photoactive compositions for use in photoresists. It would be further desirable to have new photoactive compounds that exhibit enhanced solubility in photoresist solvents and formulations.